1. Field of the Invention
This invention relates to a protective puncture and cut resistant material to protect against accidental injuries from needles, scalpel blades, knives and other sharp pointed instruments.
2. Description of the Related Art
Protection from accidental cuts and punctures is needed in the fields of medicine and law enforcement, and in any occupation where sharp instruments are encountered and where the combination of flexibility and protection against cuts and puncture wounds is needed.
Accidental needle sticks and scalpel blade cuts occur to doctors and nurses, while performing surgery, giving injections, taking blood samples, and administering intravenous liquids. The accidental needle sticks and scalpel blade cuts by themselves are harmful; however, in a medical situation a cut or puncture can also transmit infection either to the patient or to the medical person performing the procedure.
In the past, the main concern was that a surgeon would infect the patient during surgery. This is still a concern and is adequately addressed by using latex gloves. Because some people are allergic to the elastomer latex, there are various non-allergenic elastomers, such as Nitrile. Where the term latex or elastomer is used herein, the term is also meant to include various non-allergenic elastomers as well. Unfortunately, it is also increasingly crucial to protect surgeons and other medical personnel from infection. A surgeon can contract hepatitis, AIDS, and other diseases, when the blood or body fluid of a patient is transmitted through the skin of the surgeon. It is estimated that the average surgeon has about three cuts or puncture wounds per month, caused by either a hypodermic needle or a scalpel blade. This presents an unacceptable risk factor for surgeons and other medical personnel.
The CDC (Centers for Disease Control and Prevention) has estimated the number of percutaneous (through the skin) injuries per year in the United States. Each year there are 30 reported injuries per 100 occupied hospital beds. Since there are 600,000 occupied hospital beds in the United States, there are 180,000 reported percutaneous injuries reported per year. In addition the CDC estimates that 39% of the incidents are not reported according to the survey conducted. Also, the CDC doubles the resulting figure because 50% of healthcare workers are employed outside of hospital settings. The total estimated number of percutaneous injuries per year is 590,194.
The risks of infection following a single HIV (human immunodeficiency virus), HBV (hepatitus B virus), or HBC (hepatitus C virus) contaminated needlestick or sharp instrument injury are 0.3%, 6%–30%, and 1%–10%, respectively. Clearly surgeons and other health care workers are facing a high risk of infection from needlesticks and other sharp instruments.
Conventionally, surgeons and other medical personnel wear sterilized latex gloves, which are thin and flexible enough to enable a surgeon to freely manipulate his fingers, and to utilize his sense of touch. If the latex gloves are not penetrated then the patient and the surgeon are protected from infection; however, latex gloves offer hardly any protection against accidental punctures or cuts, because hypodermic needles and scalpel blades can easily puncture or cut through a latex glove. Even multiple layers of latex gloves, which medical personnel increasingly use to provide additional protection against transmission of infection, offer no protection against accidental punctures or cuts.
It is important to distinguish between cuts and puncture wounds. A cut is typically from the edge of a scalpel blade. A puncture wound can be caused by the point of a scalpel blade or by the point of a hypodermic needle. A scalpel blade is typically about 0.75 inches long with a sharpened edge and with a point about 0.001 inches in diameter. As the distance from the point increases the scalpel blade width increases. A hypodermic needle can be as small as 0.001 inches in diameter at the point, widening to about 0.010 inches half way up the bevel of the needle, and increasing to about 0.018 inches in diameter for the shaft of a No. 27 needle. It is much easier to protect against a cut from an edge of a scalpel blade than to protect against a puncture from either a scalpel blade or a hypodermic needle, because a scalpel blade has a wider surface upon which the pressure of the cut is distributed. For example, if the pressure is 2000 grams, then the pressure per square area for a scalpel blade is 2000/(0.75*0.001), assuming the edge of the scalpel blade is the same sharpness as the point of the scalpel blade (0.001 inches) and that the scalpel blade is 0.75 inches long. For a needle with a 0.001 diameter point, the same pressure would have a pressure per square area of 2000/(3.14*(0.001/2)2), which is about nine hundred and fifty five times greater than the pressure per square area for the edge of a scalpel blade. This factor is a key reason that conventional protective gloves fail to offer adequate protection against punctures.
Most accidents in the operating room occur with some significant force. For example, a surgeon turns and is wounded accidentally by the point of a needle or scalpel being handed to him by a nurse or, a surgeon while suturing slips and punctures his hand with a needle. Effective protection against punctures should protect against pressures up to approximately 1500 to 1800 grams. This level of protection is well beyond the protection provided by the conventional puncture resistant gloves.
Conventional approaches to providing increased protection beyond latex gloves against cuts and punctures for a surgeon or other medical personnel include: providing a glove with a weave or knit of a material such as Kevlar, nylon, stainless steel or fiberglass; providing reinforced areas such as on glove fingers; placing foam material between two latex gloves; and providing leather on portions of the glove. Some of the materials, such as leather and Kevlar knits provide protection against cuts, but virtually no protection against punctures.
Conventional protective gloves having a simple weave or knit of a material such as Kevlar, nylon, stainless steel or fiberglass are characterized by U.S. Pat. Nos. 4,526,828, 5,070,540, 4,833,733, 5,087,499, 4,742,578, and 4,779,290. These approaches have fairly effective protection against cuts, because a material such as a Kevlar weave is hard to cut through. However, a shortcoming of all of these approaches is that the weave or knit is simply spread apart by the wedge on a needle or scalpel point to form a passage as the needle or scalpel point is inserted into the material. Making the weave tighter or thicker does not prevent punctures; moreover, a thicker or tighter weave significantly reduces the flexibility of these gloves and their usefulness. As the number of layers or the thickness of the material increases, the ability of a surgeon to freely manipulate his fingers, and to utilize his sense of touch is significantly reduced.
Conventional protective gloves providing reinforced areas are characterized by U.S. Pat. No. 4,865,661, which has woven fiberglass placed at certain areas on the fingers of a glove and U.S. Pat. No. 5,187,815, which has corrugated metal foil in areas to be reinforced. The shortcoming of these approaches is that the reinforced areas have little flexibility so can only be placed on certain areas, which leaves the rest of the glove without the same protection. Also, even woven fiberglass and corrugated metal may be punctured. The point of a #11 blade will easily pass through metal foil ½ to 1 mil thick.
The approach of placing foam material between two latex layers is the approach of U.S. Pat. No. 4,901,372, which provides little if any protection against cuts and punctures, because the latex and the foam can be easily cut and punctured.
Providing leather on a glove is an approach that provides some protection to cuts; however, little protection to punctures. Even though the pores of the leather may be smaller than the diameter of a needle, a needle will simply make a hole in the leather as it passes through.
A flexible puncture proof material in the prior art, which has capture devices, and therefore provides protection against both cuts and puncture wounds, is described in U.S. Pat. No. 5,601,895 issued to Frank W. Cunningham, M.D. on Feb. 11, 1997, and shown in FIGS. 1–3.
FIG. 1 is an elevation sectional view of the flexible puncture proof material 10 of U.S. Pat. No. 5,601,895. The flexible puncture proof material 10 has an flexible medium 22, which surrounds and attaches to capture devices, such as capture devices 24 and 26 within the flexible medium 22. The capture devices are attached in layers to the flexible medium and the number of layers depends on the type of material used for the capture devices. The flexible medium 22, which can be a flexible polymer such as silicone elastomer, binds the capture devices in the layers together and holds them in place. The flexible medium 22 provides a barrier against the transmission of water and infection through the material.
A base layer 40 can be provided, which can be fabricated of a woven material such as a steel mesh or a Kevlar weave. Alternately, base layer 40 can be made of fabric. The purpose of the base layer 40 is to provide a spacer if capture of a sharp instrument occurs in the deepest layer of the capture devices. For example, if only three layers of capture devices are used, and capture occurs in the third layer of capture devices, then the base layer 40 would prevent a point that slightly protrudes from a capture device from penetrating the entire puncture proof material. The base layer 40 also provides greater durability to the puncture proof material. The base layer 40 is purposely porous to allow the flexible medium 22 to permeate the base layer 40. The flexible medium extends to an elastomeric layer 14 on one side of the base layer 40.
The flexible puncture proof material 10, as illustrated in FIG. 1, provides first capture layer 16, second capture layer 18, and third capture layer 20. Each capture layer is comprised of a plurality of discs or plates, which have apertures. Each aperture in each plate or disc is large enough to accept and capture the pointed end of the sharp element and small enough to prevent the sharp element from passing through the aperture, which provides protection against punctures.
As shown in FIG. 1, disc 24 is in first capture layer 16, disc 26 is in second capture layer 18, and disc 28 is in third capture layer 20. Within each disc, apertures 30 are provided. FIG. 2 is a fragmentary plan view partially cut away along line 2—2 of FIG. 1 and shows how the disc layers overlay each other.
The layers are arranged relative to one another so that, although there are spaces 31 between discs in each layer, there is no vertical path of spaces through the layers. For example, FIG. 2 shows the triangular spaces 31 between the round discs on first capture layer 16, which are effectively closed or overlapped by discs on second capture layer 18. Any remaining voids in the first two capture layers are overlapped by discs on third capture layer 20.
The plates or discs of FIGS. 1 and 2 can be fabricated from stainless steel or some other hard material. The purpose of the apertures 30 in the discs is to capture the point of a sharp instrument, such as a hypodermic needle or a scalpel.
FIG. 3 is an elevation sectional view of the flexible material of FIG. 1 showing needle 50 attempting to puncture through the flexible material 10. As shown, the needle point 52 has been captured by aperture 42 on disc 24 in first capture layer 16. The diameter 46, as shown in FIG. 1, of aperture 42 is large enough to capture the needle point 52, but small enough so that the body of needle 50 cannot pass through flexible material 10. The needle diameter 54 is larger than aperture 42. As shown in FIG. 3 the needle point 52 is about to pierce through space 44 between disc 56 and disc 26 on second capture layer 18; however, the needle 50 has already been captured by aperture 42 so will be stopped from puncturing through the material.
FIG. 3 also shows scalpel 60, which has scalpel edge 62 and scalpel point 64, attempting to puncture through the flexible material 10 at space 34 in first capture layer 16. The scalpel will pass through space 34 but will then be captured by aperture 36 on disc 26 on the overlapping second capture layer 18. The diameter 46 of aperture 36 is small enough to capture the point of the scalpel, but small enough to not allow the scalpel to pass through flexible material 10. The diameter 46 of aperture 36 is about the width of scalpel blade dimension 68, but much smaller than the scalpel body width 66. The same principle applies to stopping a puncture from a needle.
The flexible puncture proof material of U.S. Pat. No. 5,601,895 provides a much more effective puncture proof material than many other prior art designs. However, a limitation is that a completed glove using the discs with capture element holes of the prior art described above is made by fabricating patterns of the material and then joining them together. A glove cannot be made using a single stage injection molding process or a dipping process as described below, because the use of a planar unit, as described in U.S. Pat. No. 5,601,895, in an injection molding process or a dipping process would result in random orientation of the planes of the capture unit discs. The outcome if injection molding or dipping were used would be defective stacking of the discs, which would result in areas with voids.
Gould U.S. Pat. No. 5,200,263 describes a composite material for puncture resistance made of steel platelets embedded in an overlapping pattern in an elastomer. A coating of material, such as epoxy, is added to minimize “skating”. The resulting composite has a number of issues. First, planar platelets are relatively unstable to an impacting needle, even with an epoxy coating, and epoxy only increases the stiffness of the composite. Second, a needle at an oblique angle to the composite can readily spread the platelets. Third, a method described for dusting on the platelets lacks the precision and control to obtain a uniform, void-free coating, necessary to prevent injury. Many of these same concerns also apply to Gould U.S. Pat. No. 5,514,241, which describes a method of serial dipping into a suspension of platelets in elastomer. The resultant deposition and layering is random, and may produce excessive thickness or inadequate thickness of platelets. A further issue is that steel platelets, which have a specific gravity of about 9, and elastomer, which has a specific gravity of about 1.4, in a “suspension” would result in the platelets sinking, impairing uniformity of the suspension.
Samples U.S. Pat. No. 5,368,930 describes a composite material of an elastomer and non-elastomeric particles, such as metals, ceramics or crystalline minerals, especially those crystalline minerals having a plate-like nature. The described particles are very small, and would be unstable to needle impact, in large part due to their hardness, permitting tilting and deflecting of the needle point, and puncture. If the density of particles were increased to minimize this effect, there would be a proportionate increase in stiffness of the composite.
Darras U.S. Pat. Nos. 5,817,433 and 6,020,057 describe a composite made up of an elastomer with imbedded particles of very small size, 5 to 8 microns, of a very hard material, such as silicone carbide or diamond dust. The method of forming the composite is either by “dusting on” or by forming a mixture of elastomer and the particles. One or more layers of the composite can be interspersed with layers of plain elastomer. Such layering is increased depending on the puncture resistance desired. Again the hard particles would permit tilting and deflecting of the needle point, and puncture. By increasing the layers, the puncture resistance is increased, but there would be a proportionate increase in stiffness of the composite.
Thus, there is a need in the art for a puncture and cut resistant surgical glove that is flexible and protects against accidental puncture injuries from needles, scalpel blades and other sharp pointed instruments. It is desirable to form the surgical glove using low cost methods of fabrication.